A microphone is an electroacoustic transducer changing the sound wave energy into electricity. The conversion of this energy may be performed in different ways (hence the different types of microphones). The microphone is typically the first element of an audio track. Microphones can be classified into different categories based on the following criteria:
the way of processing the membrane vibrations into an electrical signal;
the nature of the sound field effects on the membrane; and
the application itself.
In the first category, the way of processing vibrations of the membrane, the following categories may be further distinguished:                carbon microphone;        piezoelectric microphone;        dynamic microphone;        condenser microphone (electret/large-diaphragm/small-diaphragm/surface); and        experimental microphones.        
The condenser microphone was first invented at Bell Labs in 1916. The structure consisted of two electrodes. One of the pads is stationary while the other pad acts as a diaphragm and is exposed to acoustic waves as shown in FIG. 1. Movement of the diaphragm creates a variable component in the DC voltage of the capacitor, which reflects the frequency of the acoustic wave incident on the microphone. For this design to work, the voltage of 48V is necessary (i.e. a phantom and it is provided with a battery or a microphone cable). Depending on whether the polarization requires an external microphone or not, the condenser microphones may be divided into externally polarized condenser microphone and electret microphones. Both types require power, as an integral part of the microphone, such as, for example, a three-microphone amplifier. In the following, the electret microphones and the externally polarized condenser microphones will be describe in detail.
In the case of making high quality recording of voice or sound of the choir (or any other group of people singing), i.e., strings or metal drums, a condenser microphone is used. This may happen for two reasons: these microphones have a generally wider and more even frequency range than dynamic microphones of comparable quality. Additionally, they do have a wider bandwidth and above all, have higher voltage sensitivity. Therefore, because of their sensitivity to loud noises, compared to dynamic microphones, they are used predominantly in the studios.
In the prior art publication CN103557929 (A) a method for making a membrane comprising graphene is disclosed. The produced membrane is then used as an element of the optical fiber system, which represent the acoustic pressure sensors. The publication KR101058475 (B1) discloses a MEMS microphone comprising a graphene diaphragm structure and a method of manufacture of graphene layers on the surface of the fixed electrode covered with polysilicone.